This invention relates to pumping apparatus and more particularly to peristaltic pumps in which fluid is directed through a compressible tube by progressively occluding the tube between preselected points along its length.
The present invention, while of general application, is particularly well suited for use in simultaneously pumping a series of fluids in predetermined relative proportions at predetermined flow rates. As is well known, pumps employed for this purpose include an array of resiliently compressible tubes which are arranged in parallel substantially coplanar relationship with each other adjacent a continuously rotating rotor assembly. The rotor assembly is provided with a plurality of rollers for simultaneously occluding the tubes between spaced points along each tube. The tubes customarily have different internal diameters to vary the volume of fluid between the occlusion points and thereby pump different quantities of fluid. For analytical purposes certain of the tubes may contain a liquid sample which is mixed with one or more reagents in other tubes to provide a particular color, the optical density of which is indicative of the concentration of a substance in the sample. The sample fluid, either before or after the addition of the reagent, is separated into sequential segments by the introduction of air or other segmentizing fluid at equally spaced intervals.
Heretofore, pumping apparatus of the foregoing type exhibited certain disadvantages. For example, in many prior peristaltic pumps difficulties were encountered in introducing the segmentizing fluid in a manner that would provide an abrupt separation between successive fluid segments. As another illustration, and this was of special moment for pumping apparatus of the type in which chain driven rollers were used to sequentially occlude and then release a series of compressible tubes, the tubes exhibited excessive wear and were subject to other malfunctions. A still further difficulty exhibited by such prior pumping apparatus was occasioned by deficiencies in the supporting structure for the rotor assembly which resulted in excess friction and wear of the individual rollers.